Curtains have been used as shading means in green-houses and shade halls for a number of years. The green-house curtain, even called the shading web, has replaced this previous common lime painting of the glass surfaces of the green-house, but has also involved other advantages. Thus it can be assured that the fall of cold which occurs when the ventilator doors are opened is eliminated and a continuous ventilation and heat distribution is obtained. Besides, the shading fabric stops the sun shine which is let in through the open ventilator doors. As a result of this the supplying of nutritive liquid to the plants cultivation can be kept more regular and at a lower level, at the same time as the difficult and risky job with the lime painting of the glass surfaces and the removal of the paint can be completely eliminated. It is also important that the green-house curtain is movable, i.e. that it is rollable and drapable, so that in a simple way it can be pulled across or aside for regulating the inlet of light, at the same time as when it is rolled up or draped does not require any considerable space.
The high costs for heating green-houses have enforced demands for a better heating insulation, and these wall linings with different type of foils alone or together with ceiling covering of a shading web, which are used up to now, gave almost unassuming heat savings. This mainly depends on the fact that the insulating efficiency of these materials are low.
Insulating is needed on different situations.
(a) for strong radiation of sun (field of wave lengths 300-2.800), PA1 (b) for low radiation during cold days to get a "positive balance of energy", i.e. the losses of heat are much higher than the profits of radiation during day time (windy, cloudy and cold days), PA1 (c) the convection losses at night, PA1 (d) heat losses by radiation at nights PA1 (e) ventilating losses at night PA1 (f) condensation losses at night PA1 (g) combination of the above PA1 (a) it should be drapable and rollable in both direction of the material path. PA1 (b) it should be substantially tight against thermal air flows, but water-transmitting, so that no water gathering occurs if the green-house curtain is arranged horizontally. PA1 (c) it should be able to be manufactured in very large widths for example 6 meters without seams. PA1 (d) it should release a certain amount of water vapour. PA1 (e) it should be durable against mechanical damage as well as UV-decomposition. PA1 (f) it should be able to be manufactured in several alternative designs, such as, high reflective low emitting, transparent, semitransparent, for certain radiation (through for example metalizing). PA1 (g) it should be able to be made two-sided, i.e. having a textile property on one side, for example the under side, and a non-textile property on the othr side, the upper side, so that the underside can bind the condensing water and the upper side can reflect solar radiation. PA1 (h) the strips should be bound together and safely fixed in a stable yarn framework.
To manage the above demands conventional textile material are not sufficient.
It is necessary to on one hand use materials which are transparent and/or reflecting for sun light and on the other hand materials which are highly reflecting or low emitting for long wave radiation. The combination of these qualities is not found in textile materials, but in foils.
A foil is however not suitable for the purpose since it is diffusion proof, gathers water pockets, fractures, decays by sun light and is very stiff for being/draped, which is the established way to apply the fabric in a green-house. Condensing drops are besides formed on the inside, which can not be allowed.
The DE-A-No.2835375 describes a crocheted fabric consisting of a net like yarn structure, in the open net loops of which are laid strips of a flexible material, for example plastic foil strips. The purpose of this technique is to achieve a greater richness of variation as regards the pattern of the fabric. Thus it is possible to use foil paths with imprinted patterns which before the introduction into the crocheted goods are cut out to strips, so that the completed goods shows the same pattern as the foil path, but optically is open-worked by the textile threads. Such a crocheted article suits for decoration purposes, such as for curtains in which the main purposes is to be decorative, but can not be used as green-house curtains, since the foil strips are arranged with relatively large spaces therebetween and therefore would allow convectional air streams, radiation and condensing water to pass through the fabric. Furthermore, the connection between the foil strips and the textile connecting threads is not such that the relatively smooth strips are fixed against displacement.
Through the Swedish patent publication No. 8001544-9 it is known to design a green-house curtain as an insulating fabric, which between the double parallel textile paths strips of a heat radiation reflective material have been placed. This double insulating fabric has certainly a very good insulating effect and reflecting efficiency, but as it requires double textile paths, which through a special arrangement are connected with each other, the manufacturing price becomes relatively high at the same time as the double paths at the rolling, draping or bringing together sideways requires a relatively large space.
It is also known through the Swiss Pat. No. 138000 to use metal foil strips for textile purposes, said strips being used in order to bring about effects of applied industrial art, such as through using the strips in twisted form or through wrapping up them about a yarn.
As for shade halls, these are used in warm countries (tropical to Mediterranean climates), in which plants are protected against strong solar radiation but convectional air streams are permitted to pass through the walls. The most primitive shade halls are built by spaced boards or bamboos. There are also known shading fabrics intended to be placed on a frame structure, said shading fabrics being made of black plastic material. The black material prevents the solar radiation from reaching the plants by absorbing it and converting it into heat radiation. This means that the temperature in the shade hall during the daytime will be high, which could be injurious to the plants. During night-time, the black material will emit much heat radiation out of the shade hall, so that the temperature therein will be low.
In French patent publication No. 2.071.064 there is disclosed a fabric which can be used for shading of plants. It is a woven fabric, in which some of the warp threads consist of flat yarns, which could have absorption and/or reflection ability. There are also other warp threads in order to provide a suitable distance between the warp threads so that a perforated fabric is obtained. All threads in the fabric are made of synthetic materials, such as polyethylene, propolyene, polyvinyl and the like. The yarn framework disclosed in this publication, however, would not be suited for providing fixation of "slippery" foil strips therein.